[development] MySQL query cache
hans at lonki.xs4all.nl
Thu Aug 30 16:50:47 UTC 2007
With all the talking about caching I would like to ask some things.
Currently I am using MyISAM tables. I have a small moodle site and
was puzzled about
the amount of memory being used. Tinkered with apache and enabled the
The last tweak, the cache, is a MySQL only thing, PostgreSQL does not
Running the site a few days I kept wondering why it still does not
really speed up. I think I now
found part of the problem. There are some tables that are unfit to be
used with the
query cache. This is not due to drupal but more to the specifics the
query cache is using.
MySQL will optimize queries and will store select queries, when
possible, in the cache. There
for it does not need to recompile/optimize the query the next time it
is called. Whenever a value
is updated or inserted in a table the queries that are questioning
these tables will be invalidated.
For a few Drupal tables this will only generate extra cpu cycles
without any benefit. Both the session and cache tables are updated
when enabled in the config on almost every page view.
A solution would be to add SQL_NO_CACHE after the selects on these
queries. This however
would break the queries for PostgreSQL.
What would be the best way to submit a patch for this?
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